1. Field of the Invention
The present invention relates to a boost circuit and an operation method for the boost circuit. In particular, the present invention relates to a boost circuit that performs a boost operation by using a charge pump, and an operation method for the boost circuit.
2. Description of Related Art
A charge pump-type boost circuit is one of basic circuits used for various devices. For example, the charge pump-type boost circuit is installed in a liquid crystal display panel drive IC (Integrated Circuit) for a cellular phone. The boost circuit boosts a supply voltage supplied from a power supply such as a battery to generate a panel-driving voltage for driving the liquid crystal display panel.
The boost circuit is required to provide a desired output voltage stably even if the supply voltage is greatly varied. A configuration of the boost circuit that satisfies such a requirement is disclosed in Japanese Patent Publication JP-2008-245500A. According to this related technique, the boost circuit monitors a sum of the supply voltage and a voltage of a boost capacitor during a period when the boost capacitor is charged and controls the charging of the boost capacitor depending on the sum. According to the control, the voltage charged to the boost capacitor is adjusted in response to the supply voltage, and thus a desired output voltage can be stably obtained for a wide range of the supply voltage.